The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device which includes a color filter forming region and color filter non-forming regions in the inside of a lighting region which is visible to a viewer within one pixel.
Since a liquid crystal display device is thin, light-weighted and exhibits the low power consumption, the liquid crystal display device is used as a display device of electronic equipments in a broad range covering a notebook type personal computer, a word processor, an electronic notebook, a mobile phone, a camera built-in video recorder and the like. Different from a cathode ray tube or a plasma display device, the liquid crystal display device is not self-luminous and displays an image or the like by controlling a light quantity of light incident from the outside. Further, by providing a plurality of color filters as light control elements to the liquid crystal display device, the liquid crystal display device can perform a color image display of multi-colors. A most popularly used liquid crystal display device is a so-called transmissive type liquid crystal display device which arranges an illumination source which is referred to as a backlight using a fluorescent tube, a light emitting diode or the like on a back surface thereof and displays images by controlling a quantity of light which passes through the liquid crystal display device out of light emitted from the backlight.
However, in this transmissive type liquid crystal display device, the power consumption attributed to the backlight occupies an approximately half of the total power consumption and hence, when the portable type electronic equipment is driven by a battery, this power consumption attributed to the backlight is a major factor which shortens the use time of the liquid crystal display device. Further, when the transmissive type liquid crystal display device is used in a bright environment such as the outdoors, an ambient light reflects on a surface of a display region and hence, it is difficult to recognize a display image.
As a liquid crystal display device which is always used in a portable manner in a bright environment such as the outdoors, there has been known a so-called reflective type liquid crystal display device which does not usually use a backlight, includes a reflection film and controls a reflection light of an ambient light from surroundings of the liquid crystal display device using a liquid crystal layer. Further, there has been also known a semi-transmissive and semi-reflective type (hereinafter also referred to as “partial transmissive type”) liquid crystal display device which performs a transmissive type display and a reflective type display using semi-transmissive and semi-reflective films. Still further, there has been also known a liquid crystal display device which forms openings in color filters for enhancing the brightness.
FIG. 9 is a schematic view for explaining the constitution of a vicinity of one pixel of a conventional liquid crystal display device, wherein FIG. 9(a) is a plan view, FIG. 9(b) is a cross-sectional view taken along a line A–A′ in FIG. 9(a), and FIG. 9(c) is a cross-sectional view taken along a line B–B′ in FIG. 9(a). The liquid crystal display device includes a large number of pixels which are arranged in a matrix array and also includes color filters of plural colors on either one of a pair of substrates. A liquid crystal layer (not shown in the drawing) is inserted into a gap defined between the pair of substrates which are laminated to each other. FIG. 9 shows only one substrate SUB1 on which the color filters are formed, wherein a light shielding film (a black matrix) BM, color filters CF and an overcoat layer OC are formed in this order.
Further, inside the light shielding film (so-called the black matrix) BM which is provided for enhancing the contrast of the pixel, a lighting region BA which is visible to a viewer is formed in one pixel. Then, in the inside of the lighting region BA, a color filter forming region CFA and opening portions of the color filter CF which constitutes a color filter non-forming regions CFN are formed.
Here, in the description of this specification, “lighting region which is visible to a viewer in one pixel” indicates a portion which substantially contributes to a display as viewed from the viewer within the pixel region. For example, when the pixel region is covered with a light shielding film as viewed from the viewer, an opening region of the light shielding film corresponds to the lighting region. When the light shielding film is not provided, a region where a pixel electrode is formed corresponds to the lighting region. However, in case of a lateral electric field method (an IPS method), the lighting region not only includes a region where the pixel electrode is formed but also portions in which liquid crystal is driven by a lateral electric field around the region and contribute to a display. With respect to a reflective-type liquid crystal display device, a partial transmissive type liquid crystal display device or the like in which a light shielding film is covered with reflective electrodes or the like, regions inside regions where the reflective electrodes are present correspond to the lighting regions. Here, in case of the partial transmissive type liquid crystal display device, transmissive regions which constitute opening portions of the reflective electrodes are also included in the lighting region.
As another conventional techniques which provide color filter forming regions and color filter non-forming regions, there has been known the technique in which the color filters are formed on only one sides of opening portions a light shielding portion of a reflective type liquid crystal display device (Japanese Unexamined Patent Publication Hei10(1998)-288706 (patent literature 1)) and the technique in which color filter non-forming regions are formed in consideration of the misalignment (the positional displacement) of one substrate having color filters and another substrate in the reflective type or the partial transmissive type liquid crystal display device (Japanese Unexamined Patent Publication 2000-29012 (patent literature 2)).
FIG. 10 is a schematic plan view for explaining the pixel structure of a conventional reflective type liquid crystal display device which is disclosed in the patent literature 1. As shown in FIG. 10, in this reflective type liquid crystal display device, the color filters CF are formed only at one sides of the opening portions (corresponding to lighting regions BA) of the light shielding film BM and each lighting region BA (opening portion) is divided into a color filter forming region CFA and a color filter non-forming region CFN. This structure brings about an advantageous effect that the brightness is enhanced due to the provision of the color filter non-forming regions CFN.
Further, the patent literature 1 also discloses the liquid crystal display device in which, by taking the positional displacement of the color filters CF into consideration, the color filters CF are formed such that the color filters CF cover both ends, that is, left and right ends (in the drawing) of the respective lighting regions BA so that color filter openings which constitute color filter non-forming regions CFN are formed at the center or the like of the lighting regions BA. This structure is substantially equal to the structure shown in FIG. 9 in the technical concept.
FIG. 11 is a schematic plan view for explaining another pixel structure of the conventional liquid crystal display device which is disclosed in the patent literature 2. In the reflective type or partially transmissive type liquid crystal display device shown in FIG. 11, the misalignment of the color filter CF is taken into consideration at the time of providing the color filter non-forming regions CFN in the inside of one pixel. The color filter CF having a narrower width than the lighting region BA is formed at the center thus forming the color filter forming region CFA at the center of the lighting region BA and forming the color filter non-forming regions CFN at both ends, that is, at left and right ends. In this case, even when the misalignment of the color filter CF occurs, the total area of the color filter non-forming regions CFN is fixed or constant.
FIG. 12 is a schematic plan view for explaining still another pixel structure of the conventional liquid crystal display device disclosed in the patent literature 2. In this liquid crystal display device, the color filter CF has a cruciform and the color filter non-forming regions CFN are arranged at four corners. Also in this case, even when the misalignment of the color filter CF occurs, the total area of the color filter non-forming regions CFN is fixed or constant.